Novel peptide sequence ("IQ-tag") with high affinity for NIR fluorochromes allows protein and cell specific labeling for in vivo imaging

Probes that allow site-specific protein labeling have become critical tools for visualizing biological processes. Here we used phage display to identify a novel peptide sequence with nanomolar affinity for near infrared (NIR) (benz)indolium fluorochromes. The developed peptide sequence ("IQ-tag") allows detection of NIR dyes in a wide range of assays including ELISA, flow cytometry, high throughput screens, microscopy, and optical in vivo imaging. The described method is expected to have broad utility in numerous applications, namely site-specific protein imaging, target identification, cell tracking, and drug development.